The invention relates to a wireless local area network (WLAN), and more particularly to a handover mechanism for a mobile station in a WLAN.
This section is intended to introduce the reader to various aspects of the art, which may be related to various aspects of the invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of related art.
In a mobile station (MS), such as a mobile phone, rather than a base station (BS), initiates a handover operation in a conventional handover mechanism. The mobile station gathers information to determine a time and target for performing a handover.
A conventional mobile station is capable of operating in normal and search modes. Referring to FIGS. 1A and 1B, a mobile station operating in normal mode can receive and/or place a call. When the mobile station operates in normal mode (step S102), the mobile station periodically receives beacons from a base station (BS) (step S104), while the mobile station is connected to the base station (hereinafter referred to as a current base station). In step S106, the mobile station determines a signal strength corresponding to the current base station. In step S108, it is determined whether signal strength determined in step S106 is stronger than a first threshold (TH1), and if so, the mobile station remains in normal mode, if not, step S112 proceeds. In step S112, the mobile station switches to search mode. In search mode, the mobile station receives beacons from an adjacent base station X (step S116), and determines signal strength corresponding to the base station X (step S118). In step S120, it is determined whether the signal strength determined in step S118 is stronger than a second threshold (TH2), and if so, the method proceeds to step S123, and otherwise, the method returns to step S116 to continue searching other channels. In step S123, it is determined whether the base station X is the current base station. If the base station X is the current BS, the mobile station switches back to normal mode (step S126). If signal strength corresponding to the base station X is stronger than TH2, and the base station X is different form the current BS, the mobile station hands over to the base station X (step S124).